The lamp can be found on the rear of vehicles. They are used as a convoy lights to enable vehicles to follow each other in tactical situations. The badges on the button are Green Howards (There was 1,5,6, and 7 Battalions in France). The other one looks like The King's Own Yorkshire Light Infantry (1 and 2/4 Battalions were in France during 1940). Nice little cache you found there matey.
Thank you Drew ! , the lamp i found nearby on one street was at the surface. . The 2 buttons was in same post .
That 'Black out tail signal' was puzzling me. British black-out precautions in 1940 consisted mostly of manilla paper masks and paint. I have also never seen transparent plastic on British vehicles of that period. However, the wording is easy to 'Google' and it turns out to be a later U.S. part as used on Harley Davidsons (and perhaps other vehicles) and still available as 'New Old Stock' flathead I'd guess therefore that it comes from a U.S. vehicle during the liberation period.
It's a bog standard US Army WW2 tail light, used on everything from jeeps to tanks I've never seen a U.S. vehicle from behind. Just like 21st Army Group, I'm always in front of 'em !